Neither Holmes nor Clemens was rejecting everything about phrenology. They were most concerned about phrenology’s craniological tenets – the unsubstantiated idea that small bumps and depressions on the skull can reliably reflect the growth and development of underlying parcels of brain tissue and reveal the organs of mind. They did, however, seem to accept the concept of many independent organs of mind, though not necessarily the ones listed by Gall or others. They also bought into the idea that the front of the brain is more intellectual than its posterior. Additionally, they agreed that character traits are inborn, stable, and run in families and that juries should consider the state of a criminal’s brain. Moreover, neither man had any use for metaphysics. Interestingly, Holmes saw phrenology as a branch of anthropology (broadly defined). As he put it: “Strike out the false pretensions of phrenology, call it anthropology; let it study man the individual in distinction from man the abstraction … and it becomes the proper study of mankind, one of the noblest and most interesting of pursuits.” Twain was also fascinated by the diversity he observed among his fellow human beings, and also felt the family of man deserved further study.

Holmes and Clemens wanted to educate the public about the head reading fad. But Clemens was taking on a less controversial topic when Mark Twain began to assail the head readers during the 1870s. By this time, Paul Broca had shown that the clinical-pathological method could delineate a brain region for fluent speech. Further, Fritsch and Hitzig in Germany and David Ferrier in England were now discovering special forebrain areas for voluntary movements, the different sensory systems, and even higher functions by stimulating different parts of the brain in animals and making lesions. Holmes did not recognize these better ways to understand the mind and brain when he began to lampoon phrenology in 1859. Thus, there was a great scientific divide separating what Holmes and Clemens did, even though both men shared similar objectives and helped take the luster out of head readings. I conclude with the thoughts that popular literature can be a valuable tool for appreciating scientific and medical developments, and that Holmes and Clemens were right not to paint with too broad a brush. True, phrenological craniology deserved to be ridiculed, but phrenology also had positive features that would become fundamental tenets of psychology and the neurosciences.